Magnetic storage systems, such as a hard disk drive, are utilized in a wide variety of devices in both stationary and mobile computing environments. Examples of devices that incorporate magnetic storage systems include desktop computers, portable notebook computers, portable hard disk drives, digital versatile disc (DVD) players, high definition television receivers, vehicle control systems, cellular or mobile telephones, television set top boxes, digital cameras, digital video cameras, video game consoles, and portable media players.
A typical hard disk drive includes magnetic storage media of one or more flat disks. The disks are generally formed of two main substances, namely, a substrate material that gives it structure and rigidity, and a magnetic media coating that holds the magnetic impulses or moments that represent data. A hard disk drive also typically includes a read head and a write head, generally a magnetic transducer which can sense and/or change the magnetic fields stored on the disks. Perpendicular magnetic recording (PMR) involves recorded bits that are stored in a generally planar recording layer in a generally perpendicular or out-of-plane orientation. A PMR read head and a PMR write head are usually formed as an integrated read/write head on an air-bearing slider. In a PMR reader, a tunnel magnetoresistance (TMR) sensor is frequently employed in the read head.
Hard disk drive performance demands and design needs have intensified. The current demand for larger capacity in a smaller dimension is linked to the demand for ever increasing storage track density. As the density of data on the magnetic storage medium increases, the strength of the magnetic fields generally decrease, in order to minimize interference. Higher areal density in magnetic storage medium requires advanced read/write transducer design.